1. Field of Invention
The present invention relates to a viscous fluid coupling device of the type including temperature responsive bimetal elements, and more particularly, to an elastic mounting arrangement for the free end of the bimetal element.
2. Description of the Prior Art
Viscous fluid coupling devices of the type to which the present invention relates are now well known in the art and may be better understood by reference to U.S. Pat. No. 3,227,254.
Although the present invention may be useful with many types and configurations of temperature responsive fluid couplings, it is especially advantageous on those to be used with vehicle radiator cooling fans, and will be described in connection therewith.
A typical fluid coupling device includes an output coupling member and a cover member cooperating to define a fluid chamber. The device includes a valve plate disposed to separate the fluid chamber into a reservoir and an operating chamber. An input coupling member is rotatably disposed within the operating chamber and the device includes valve means operable to control the flow of fluid between the reservoir and the operating chamber. The valve means includes a valve shaft extending outwardly through the cover means and being rotatable relative thereto. The rotational position of the valve shaft and the valve is controlled by a temperature responsive bimetal element having a first end portion connected to the valve shaft and a second end portion fixed relative to the cover means.
A problem which has arisen in connection with the use of viscous fluid couplings on four-cylinder engines relates to the greater vibration inherent in four-cylinder engines. The engine vibration is transmitted to the fluid coupling and typically, the result is excessive wear between the bimetal element and the shaft and between the bimetal element and its mounting bracket. If excessive wear occurs at either of these locations, there may be a substantial change in the temperature at which the coupling engages and/or disengages, causing unsatisfactory operation of the device.
If the wear becomes extreme, especially between the bimetal coil and the shaft, the coil may become completely detached from the device, with the result that the device will no longer be temperature responsive, but will remain either engaged or disengaged, whichever was the condition of the device at the time that the coil become detached.
A resilient supporting arrangement of the free end of the coil is found, for instance, in the U.S. Pat. No. 4,103,765 wherein the free end of the coil is resiliently retained to the clip by means of the resilient material. This resilient material is associated with the bimetal to retain the free end at a given position relative to the slot in the clip and resiliently restricts radial movement of the free end from the give portion. Such a conventional resilient supporting arrangement is complicated in structure. In addition, a die has to be used to form the resilient material.